Inverse mask generating printer and printer module

ABSTRACT

An inverse mask image generating printer and printer module are provided. In one aspect, an inverse mask image generating module has an input adapted to receive the image data for an image to be printed said image data having color data for a first set of colors used in a first color model; an inverse mask image processor generating an inverse mask image using color data for one of the first set of colors; and an output providing the inverse mask image for use by a print engine. The inverse mask image is generated based upon the color data for a selected one of the first set of colors so that the inverse mask image can be generated without first determining color separation toner images that define amounts of color toner to be applied to form the elements of the image.

CROSS REFERENCE TO RELATED APPLICATIONS

This application relates to commonly assigned, copending U.S.application Ser. No. 12/908,916, filed Oct. 21, 2010, entitled: “METHODSFOR GENERATING AN INVERSE MASK” which is hereby incorporated byreference.

FIELD OF THE INVENTION

This invention pertains to the field of printing.

BACKGROUND OF THE INVENTION

In an electrophotographic modular printing machine of known type, forexample, the NexPress 2100 printer manufactured by NexPress Solutions,Inc., of Rochester, N.Y., color toner images are made sequentially in aplurality of color imaging modules arranged in tandem, and the tonerimages are successively electrostatically transferred in registration toa surface that is moved past the imaging modules. This transfer can bemade to receiver member that is moved past the imaging modules or to anintermediate transfer member that receives all of the toner images to beused in an image and then transfers these to a receiver member that ismoved through a transfer nip. After all of the toner images have beentransferred to the receiver member, the receiver member is fused.

As is known, when the color toners are deposited one upon the other, therespective color toners form toner stacks that will create particularcolors at particular locations of the image formed on the receivermember after fusing. The height of a respective color toner stack is thesum of the toner contributions of each color of toner applied at aparticular location. FIG. 1 depicts an exemplary section of a receivermember 2 having a plurality of color toner stacks 4A-4N before a fusingoperation. As can be seen from FIG. 1, color toner stacks 4A-4N providea range of color toner stack heights before fusing, with the toner stackheights varying based upon the amount of a particular color tonerapplied thereto.

FIG. 2 shows the section of FIG. 1 after fusing. As can be seen in FIG.2, color toner stacks 4A-4N typically flatten to form a toner mass 6because of the pressure and heat applied during fusing. However, reliefdifferences remain on upper surface 8 of toner mass 6 between, forexample, an area 10 that corresponds to high density color imageelements shown in FIG. 1 as having higher toner stack heights e.g. tonerstack 4D and an area 12 that corresponds to lower density color imageelements shown in FIG. 1 as having a lower toner stack height e.g. tonerstack 4E in FIG. 1. These variations are particularly noticeable in thatthey disrupt the extent to which surface 8 of a toner printed imagereflects light in a specular manner. The capability of a printed imageto reflect incident light in a specular fashion is typically referred toas gloss.

In a fused toner image, several factors impact gloss. The primaryfactors indicate the refractive index of the fused toner and the surfaceroughness of the fused toner. It will be appreciated that more uniformgloss can therefore be provided on an image by forming a toner imagewith an upper most surface having less surface roughness.

Electrostatographic printers having a three, four, or more color(multicolor) capability are known to also provide an additional tonerdepositing assembly for depositing clear toner. U.S. Pat. No. 5,234,783,issued on Aug. 10, 1993, in the name of Yee S. Ng, et al., describes aprocess where gloss of a printed image is improved by applying glossimproving clear toner image to the color toner stacks forming the image.The gloss producing clear toner image varies inversely according to theexpected stack heights provided by the other images providing ultimatelyan even height toner image. Similarly, U.S. Pat. No. 7,016,621, issuedon Mar. 21, 2006 in the name of Yee S. Ng, describes the formation of atoner image wherein back-transfer artifacts are reduced or eliminatedwithout the need or expense of providing uniform coverage of clear tonerto the print wherein a five color tandem printer is used to print fewerthan five colors. The fifth station may be used during the one passthrough the printer apparatus, as a clear toner station, to depositrelatively less clear toner in relatively higher colored areas andrelatively more clear toner in areas having relatively lower amounts ofcolored toner.

Such gloss improving clear toner images are also known in the art andreferred to as inverse mask toner images. As is noted in the '783patent, inverse mask toner images can be recorded, for example, on topof the color toner stacks or beneath the color toner stacks.

Methods for determining the inverse mask, however, have remainedcomputationally intense in that, in general, an amount of clear toner tobe laid down is calculated for each pixel location in the toner imageformed by the multi-layer toner image. See for example, commonlyassigned U.S. Pat. No. 7,236,734, entitled Method and Apparatus forElectrostatographic Printing With Enhanced Color Gamut, issued to Ng. onJun. 26, 2007. As is described therein, incoming image data to beprinted is input to a Raster Image Processor and converted to printerdependent color separation image data in each of the four-color imagesprinted by the printer apparatus. The clear toner image generator, whichalso may be a part of the RIP, creates a clear toner “image” from thefour color separation images previously created assuming that glossingis to be done and an inverse mask is to be established for printing ofthe clear toner.

It is further noted in the '734 patent, that, as a convenience incalculation, rather than determining pigmented toner coverage at anypixel area in accordance with the sum of the four color contributions atthat pixel location, one may select the maximum pixel percentcontribution by a color separation at that pixel location as thepercentage of pigmented toner coverage present at that location for usein determining the amount of clear toner overcoat to be applied in theinverse mask. The use of the single color that is maximum at thatlocation in conjunction with the particular selected inverse maskcurve's roll off starting at the mid-tone helps ensure that total tonercoverage of the four colors plus clear toner at the pixel location isbelow 320%, and this is basically true for the entire color gamut. As afurther convenience in calculation, in lieu of making such calculationfor the inverse mask using a pixel by pixel calculation, one may grouplocal areas of say 4.times.4 pixels or 16 pixels to determine the amountof clear toner in the inverse mask calculation for this small areaformed by a group of pixels.

Accordingly, using such techniques, the process of determining aninverse mask is performed after a raster imaging process performs colorseparation on the supplied image.

Further, to the extent that an image data is submitted for printing in aformat that is not readily processed by conventional raster imageprocessors, it may further be necessary to convert digital image datasupplied for printing into a format that is preferred by the RasterImage Processor. For example, it may necessary to convert submittedimage data that is organized according to one color model into imagedata that is organized according to a different model. In suchsituations, it can be necessary to first convert the submitted imagedata into a data format that can be readily processed by the RasterImage Processor. Accordingly, in such a situation, two conversion stepscan be required before the inverse mask image can be generated.

In most applications such conversions can be executed in a timely,technically, commercially, and economically feasible manner.

However, in some circumstances, for example, where images are beingprinted that incorporate variable data that can change from print toprint, there can be very little time available to process the image databefore it is used for printing. In such circumstances, it can bebeneficial to have a printer and method that enable the creation of agloss improving inverse mask without requiring generation of a tonerimage for each color non-masking toner layer.

Accordingly, what are needed are new printers and methods fordetermining an inverse mask toner image.

SUMMARY OF THE INVENTION

An inverse mask image generating printer and printer module areprovided. In one aspect, an inverse mask image generating module isadapted for use in a printer having a source of image data for an imageto be printed and a print engine for recording toner images on areceiver. The image data provides color data for a first set of colorsof a first color model. The inverse mask generating module has an inputadapted to receive the image data for an image to be printed from thesource of image data said image data having color data for a first setof colors used in a first color model; an inverse mask image processorgenerating an inverse mask image using color data for one of the firstset of colors; and an output providing the inverse mask image for use bythe print engine. The inverse mask image is generated based upon thecolor data for a selected one of the first set of colors so that theinverse mask pattern can be generated without first determining colorseparation toner images that define amounts of color toner to be appliedto a receiver to form the image.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plurality of color toner stacks on a receiver with aclear toner layer formed on top of each toner stack.

FIG. 2 shows the toner stacks of FIG. 1 in a fused state.

FIG. 3 shows a system level illustration of one embodiment of anelectrophotographic printer.

FIG. 4 shows one embodiment of a method for operating a printerincluding determining an inverse mask image.

FIG. 5 shows one embodiment of an inverse mask image generating modulefor a printer.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3 is a system level illustration of a printer 20. In the embodimentof FIG. 3, printer 20 has a print engine 22 of electrophotographic typethat deposits a toner 24 to form a toner image 25 in the form of apatterned arrangement of toner stacks. Toner image 25 can include anypattemwise application of toner 24 and can be mapped according to datarepresenting text, graphics, photo, and other types of visual content,as well as patterns that are determined based upon desirable structuralor functional arrangements of the toner 24.

Toner 24 is a material or mixture that contains toner particles and thatcan form an image, pattern, or indicating when electrostaticallydeposited on an imaging member including a photoreceptor,photoconductor, electrostatically-charged, or magnetic surface. As usedherein, “toner particles” are the marking particles electrostaticallytransferred by print engine 22 to form a pattern of material on areceiver 26 to convert an electrostatic latent image into a visibleimage or other pattern of toner 24 on receiver. Toner particles can alsoinclude clear particles that have the appearance of being transparent orthat while being generally transparent impart a coloration or opacity.Such clear toner particles can provide for example a protective layer onan image or can be used to create other effects and properties on theimage. The toner particles are fused or fixed to bind toner 24 to areceiver 26.

Toner particles can have a range of diameters, e.g. less than 8 μm, onthe order of 10-15 μm, up to approximately 30 μm, or larger. Whenreferring to particles of toner 24, the toner size or diameter isdefined in terms of the median volume weighted diameter as measured byconventional diameter measuring devices such as a Coulter Multisizer,sold by Coulter, Inc. The volume weighted diameter is the sum of themass of each toner particle multiplied by the diameter of a sphericalparticle of equal mass and density, divided by the total particle mass.Toner 24 is also referred to in the art as marking particles or dry ink.In certain embodiments, toner 24 can also comprise particles that areentrained in a wet carrier.

Typically, receiver 26 takes the form of paper, film, fabric,metallicized or metallic sheets or webs. However, receiver 26 can takeany number of forms and can comprise, in general, any article orstructure that can be moved relative to print engine 22 and processed asdescribed herein.

Returning again to FIG. 3, print engine 22 is used to deposit one ormore applications of toner 24 to form toner image 25 on receiver 26. Atoner image 25 formed from a single application of toner 24, forexample, can provide a monochrome image or layer of a structure.

A toner image 25 formed from more than one application of toner 24,(also known as a multi-part image) can be used for a variety ofpurposes, the most common of which is to provide toner images 25 withmore than one color. For example, in a four color image, four tonershaving subtractive primary colors, cyan, magenta, yellow, and black, canbe combined to form a representative spectrum of colors. Similarly, in afive color image various combinations of any of five differently coloredtoners can be combined to form other colors on receiver 26 at variouslocations on receiver 26. That is, any of the five colors of toner 24can be combined with toner 24 of one or more of the other colors at aparticular location on receiver 26 to form a color different than thecolors of the toners 24 applied at that location.

In addition to adding to the color gamut, the fifth color can also be aspecialty color toner or spot color, such as for making proprietarylogos or colors that cannot be produced with only CMYK colors (e.g.metallic, fluorescent, or pearlescent colors), or a clear toner ortinted toner. Tinted toners absorb less light than they transmit, but docontain pigments or dyes that move the hue of light passing through themtowards the hue of the tint. For example, a blue-tinted toner coated onwhite paper will cause the white paper to appear light blue when viewedunder white light, and will cause yellows printed under the blue-tintedtoner to appear slightly greenish under white light.

In the embodiment that is illustrated, a primary imaging member (notshown) such as a photoreceptor is initially charged. An electrostaticlatent image is formed by image-wise exposing the primary imaging memberusing known methods such as optical exposure, an LED array, or a laserscanner. The electrostatic latent image is developed into a visibleimage by bringing the primary imaging member into close proximity to adevelopment station that contains toner 24. The toner image 25 on theprimary imaging member is then transferred to receiver 26, generally bypressing receiver 26 against the primary imaging member while subjectingthe toner to an electrostatic field that urges toner 24 forming tonerimage 25 onto receiver 26. Toner image 25 is then fixed or fused toreceiver 26 using a fuser 60 to become a print 70. An optional finishingsystem 74 is provided to receive print 70 and to perform additionalfinishing operations on such fused print 70 such as collating, stacking,folding, binding and stapling as may be required.

In FIG. 3 print engine 22 is illustrated as having an optionalarrangement of five printing modules 40, 42, 44, 46, and 48, also knownas electrophotographic imaging subsystems arranged along a length ofreceiver transport system 28. Each printing module delivers a singleapplication of toner 24 to a respective transfer subsystem 50 inaccordance with a desired pattern as receiver 26 is moved by receivertransport system 28. Receiver transport system 28 comprises a movablesurface 30 that positions receiver 26 relative to printing modules 40,42, 44, 46, and 48. In this embodiment, movable surface 30 isillustrated in the form of an endless belt that is moved by motor 36,that is supported by rollers 38, and that is cleaned by a cleaningmechanism 52. However, in other embodiments receiver transport system 28can take other forms and can be provided in segments that operate indifferent ways or that use different structures. In an alternateembodiment, not shown, printing modules 40, 42, 44, 46 and 48 can eachdeliver a single application of toner 24 to a composite transfersubsystem 50 to form a combination toner image thereon which can betransferred to a receiver.

Printer 20 is operated by a printer controller 82 that controls theoperation of print engine 22 including but not limited to each of therespective printing modules 40, 42, 44, 46, and 48, receiver transportsystem 28, receiver supply 32, transfer subsystem 50, to form a tonerimage 25 on receiver 26 and to cause fuser 60 to fuse toner image 25 onreceiver 26 to form prints 70 as described herein.

Printer controller 82 operates printer 20 based upon input signals froma user input system 84, sensors 86, a memory 88 and a communicationsystem 90. User input system 84 can comprise any form of transducer orother device capable of receiving an input from a user and convertingthis input into a form that can be used by printer controller 82. Forexample, user input system 84 can comprise a touch screen input, a touchpad input, a 4-way switch, a 6-way switch, an 8-way switch, a stylussystem, a trackball system, a joystick system, a voice recognitionsystem, a gesture recognition system or other such systems. Sensors 86can include contact, proximity, magnetic, or optical sensors and othersensors known in the art that can be used to detect conditions inprinter 20 or in the environment-surrounding printer 20 and to convertthis information into a form that can be used by printer controller 82in governing printing, fusing, finishing or other functions.

Memory 88 can comprise any form of conventionally known memory devicesincluding but not limited to optical, magnetic or other movable media aswell as semiconductor or other forms of electronic memory. Memory 88 canbe fixed within printer 20 or removable from printer 20 at a port,memory card slot or other known means for temporarily connecting amemory 88 to an electronic device. Memory 88 can also be connected toprinter 20 by way of a fixed data path or by way of communication system90. Memory 88 can contain image data, suitable tables and controlsoftware that is executable by printer controller 82.

Communication system 90 can comprise any form of circuit, system ortransducer that can be used to send signals to or receive signals frommemory 88 or external devices 92 that are separate from or separablefrom direct connection with printer controller 82. Communication system90 can connect to external devices 92 by way of a wired or wirelessconnection. In certain embodiments, communication system 90 can compriseany circuit that can communicate with one of external devices 92 using awired connection such as a local area network, a point-to-pointconnection, or an Ethernet connection. In certain embodiments,communication system 90 can alternatively or in combination providewireless communication circuits for communication with separate orseparable devices using, for example, wireless telecommunication orwireless protocols such as those found in the Institute of Electronicsand Electrical Engineers Standard 802.11 or any other known wirelesscommunication systems. Such systems can be networked or point to pointcommunication.

External devices 92 can comprise any type of electronic system that cangenerate signals bearing data that may be useful to printer controller82 in operating printer 20.

Printer 20 further comprises an output system 94, such as a display,audio signal source or tactile signal generator or any other device thatcan be used by printer controller 82 to provide human perceptiblesignals for feedback, informational or other purposes.

It will be appreciated that printer 20 can receive image data forprinting from a variety of sources. In the embodiment of FIG. 3, thesesources include memory 88, communication system 90, that printer 20 canreceive such image data through local generation or processing that canbe executed at printer 20 using, for example, user input 84, outputsystem 94 and printer controller 82. For convenience, these sources arereferred to collectively herein as source of image data 108. It will beappreciated, that this is not limiting and that source of image data 108can comprise any electronic, magnetic, optical or other system known inthe art of printing that can be incorporated into printer 20 or that cancooperate with printer 20 to provide a information from which image datacan be determined.

In the embodiment of printer 20 that is illustrated in FIG. 3, printercontroller 82 has a color separation image processor 110 to convert theimage data into color separation images and an inverse mask processor112 to use the image data to generate inverse mask image that can beused by the print modules 40-48 of print engine 22 in generating tonerimages. An optional half-tone processor 114 is also shown that canprocess the color separation images and inverse mask images according toany half-tone screening requirements of print engine 22. The operationof these processors will be discussed in greater detail below.

Method for Printing with an Inverse Mask

FIG. 4 shows a flow chart depicting first method for printing an imagehaving an inverse mask. As is shown in the embodiment of FIG. 4, in afirst step, a print order is received including information from whichan image to be printed can be determined (step 120). The print order canbe received by source of image data 108. The print order can take anyknown form.

In the embodiment illustrated in FIG. 3, source of image data 108 cancomprise any or all of printer controller 82, user input system 84, ormemory 88 from communication system 90. As is shown in the embodiment ofFIG. 3, in a first step, a print order is received. The print orderincludes at least some data from which printer controller 82 candetermine image data for printing and can optionally include productiondata from which the manner in which the image data is to be printed canbe determined. The production data can also optionally include finishingdata that defines how the printed image is to be processed afterprinting.

The print order information is typically generated external to printer20. In one example, an external device 92 can comprise what is known inthe art as a digital front end (DFE), which is a computing device thatcan be used to provide an external source of print order information,including image data. Print order information that is generated by suchan external device 92 is received at communication system 90 which inturn provides the print order information to printer controller 82.

Similarly, the print order or portions thereof including image data andproduction data can be determined from data in any other source that canprovide such data to printer 20 in any other manner, including but notlimited receiving print order information from a portable memorysolution that is connected to memory 88.

In certain embodiments image data and/or production data or certainaspects thereof can be generated by printer 20 such as by use of userinput system 84 and an output system 94. In one embodiment of this typedigital image mastering and/or editing software can be executed printercontroller 82 at printer 20. In other embodiments of this type, adigital front end or portions thereof can be incorporated into printer20. Input system 84 and output system 94 can also be used to make localedits or modifications to the image data such as may be necessary oruseful in customizing the image data for printing using printer 20.

Printer controller 82 uses the information in the print orderinformation to determine the image data for printing (step 122). Ingeneral, the determined image data includes the entirety of what is tobe printed on a receiver by printer 20 and can comprise any pattern thatcan be provided by delivering one or more applications of toner to areceiver. In this regard, the print order information can generallycomprise any type of data or instructions that printer controller 82 canuse to locate, obtain, calculate or otherwise provide or make availableimage data for an image to be printed. For example, and withoutlimitation, the print order can include the image data for printing andthis image data can be used for printing. In another example, the printorder information can include instructions or data that will allowprinter controller 82 and communication system 90 to obtain an imagedata file from external devices 92.

Further, in other embodiments the print order information can containdata from which printer controller 82 can determine image data forexample using an algorithm, mathematical formula or other formula orlogical construct. Sill further and without limitation, the determinedimage data can include image data assembled, aggregated, compiled, orintegrated from separate data files and/or separate locations and/orother types of information that can be used to obtain, calculate orderive the determined image data or portions thereof.

The determined image data includes color information that is expressed,encoded or otherwise provided in the context of a color model that usesa first set of colors to express image information. For example digitalimages are typically encoded using a Red, Green and Blue (RGB) colormodel. The RGB color model is an additive color model in which red,green, and blue light are added in various intensities together toreproduce a broad spectrum of colors. The RGB color model is the colormodel used in most digital image and digital video capture, processingand soft presentation data formats, including the ubiquitous PEG, TIFFand MPEG formats. Most digital images are generated and shared informats that use the RGB color model.

However, most forms of printing work in a subtractive manner, that iscolors are formed by applying substances such as colored toner thatabsorb certain wavelengths of light such that only certain colors arereflected by the receiver. Because of this difference, the RGB colormodel image data is typically converted into a subtractive color modelto enable printing. One color model that is frequently used for printingis the cyan, magenta, yellow and black color model (CMYK). It will beappreciated that the determined image data can have color informationthat is encoded according to different color models. It also will beappreciated that such other types of color models can express color inways that are generally equivalent to and can be readily converted intoor understood in the context of a first color model having image datafor a first set of colors.

Printing instructions can also be determined by printer controller 82when the image data is determined. As is noted generally above, printinginstructions can comprise any information or data of any type or form,including algorithms, formula and logical processes that can inform,contribute to or otherwise help printer controller 82, color separationimage processor 110, inverse mask image processor 112 and/or half-toneprocessor 114 to, in any way, make any decision regarding how the imagedata is to be converted from image data into patterns of toner that arerecorded on a receiver by printer 20 during the printing of the imagedata. For example, the printing instructions can provide informationfrom which printer controller 82 can determine printing instructionssuch as whether to form an image on a receiver having a high glossfinish, a matte gloss finish or some intermediary finish or specificinstructions regarding whether an inverse mask is to be used in printingan image.

In still other embodiments, the print order information can include datafrom that can be used by communication system as to obtain the printinginstructions from an external device 92.

In one embodiment the print order information has data recorded thereinincluding record fields or other types of data that define or that canbe interpreted to define one or more printing instructions. In otherembodiments, signals from user input system 84 can be used as the basisfor determining the printing instructions.

In still other embodiments, printing instructions can be determined byanalysis of the determined image data such as may occur by determiningan aspect ratio for the determined image and determining printinginstructions, for example, based upon the aspect ratio and a requiredsize of the receiver. The printing instructions can also be determinedbased upon analysis of other print order information. For example, theprint order can include data or instructions from which a receiverlength, width, type or quantity can be calculated or otherwiseautomatically determined, or data indicating a location from which suchdata can be determined, calculated, or obtained by printer controller 82such as by way of communication system 90.

The determined image data and, optionally, any determined printinginstructions are made available to a color separation image generatingprocess (130) and to an inverse mask determining process (step 140).

During the color separation image generating process 130, a colorseparation image processor 110 performs a color separation process (step136) that converts the image data for the image to be printed into colorseparation images for colors of a second set of colors in the toner usedby a print engine in forming the printed image. The color separationimages define amounts of color toner to be applied to a receiver to formthe elements of the image. During the color separation process (step136) color separation images are defined so that when toner layers ofthe colors of the second set are delivered in registration according tocolor separation images and fused together, the color toner forms animage that has an appearance that corresponds to the appearance calledfor in the determined image data. Techniques for color image separationare well known in the art.

As is shown in FIG. 4, the color separation image generating process 130can also optionally use other types of image processing. These caninclude are but not limited to color conversion (step 134) and othertypes of additional image processing (step 136). Color conversion (step134) can be performed where determined image data that converts imagedata having a first color model into image data according to a secondmodel that uses a second set of colors to represent the image data.Typically, color conversion (step 134) is done to provide image datahaving a preferred color model when determining the color separationimages (step 136). For example, image data for printing can be convertedfrom the RGB color model into the CMYK color model. This can be done ina conventional manner. In a printer 20 having a print engine 22 thatuses cyan, magenta, yellow and black toners to form images, theconverted image data can be readily used to form toner images that canbe recorded by printing modules 40-46. This too is done in aconventional manner.

Additional image processing (step 136) can also be performed. Suchadditional image processing (step 136) can comprise, for example, colorcorrection or adjustment according to unique characteristics of printer20 or print engine 22 in order to obtain the desired colors in view ofthe unique characteristics of print engine 22. As is known in the art,the use of a clear toner inverse mask toner image as an overcoat on thecolor image can impact color gamut. Where it is determined that aninverse color mask is to be used (step 124), color gamut of the colortoners can be modified to reflect such adjustments. Examples of suchadjustments are known in the art and are described for example, in U.S.Pat. No. 7,324,240, entitled: “Color Correction Method with TransparentToner Insignia Images”, issued to Yee Ng on Jan. 29, 2008. This patentdescribes, generally, a method for color correction of an image havingan insignia portion in a multi-module printer. In the steps describedtherein a first color profile is calibrated for a four-color image and asecond color profile is calibrated for a four-color image with atransparent toner layer on top of the insignia portion of the four-colorimage. A plurality of image data is buffered in a color input bandbuffer. The plurality of image data is processed in the color input bandbuffer through the first and second color profiles in a color managementmodule and the processed image data is in an output band buffercorresponding to image data processed through each color profile. Aclear toner input band data stored in a clear toner input band buffer iscompared with the processed image data in each output band buffer toselect an output signal on a per pixel basis to send to the multi-moduleprinter. Additional image processing can include applying anyinstructions for modifying the image information in accordance with theproduction data.

When this method is used with a printer that is capable of forming fivetoner images, such as EP printer 20 of the embodiment of FIG. 3, colorseparation image processor 110 generates color separation images foreach toner used in one of print modules 40-48 used for color printing ofthe image data. For example, to the extent that printing modules 40-46create toner images using toners of a second set of colors includingrespectively, black, magenta, yellow and cyan, color separation imageprocessor 100 will create color separation image data for each of thesecolors. Methods for determining color separation images of this type arewell known in the printing arts and the particular method selected isnot critical here.

In many cases, the color separation images are created in the form ofwhat is known in the art as a continuous tone image. Where print engine22 has printing modules 40-48 that are adapted to record images usinghalf-tone screened images, color separation image process 130 will alsoinclude a step 138 for converting the color separation images intohalf-tone color separation images. Accordingly, during the half-tonescreening process (step 138) color separation image data is provided tohalf-tone processor 114. Half-tone processor 114 processes the colorseparation image data to form half-tone screen separation images forprinting using modules 40-46 for the toner of the respective color usedby modules 40-46. Any known half-tone screening process that iscompatible with any embodiment of a print engine 22 can be used.

Printer controller 82 can be programmed or otherwise made operative todecide whether the toner image formed using color toner is to be formedin registration with clear toner having an inverse mask (step 124). Inone embodiment, this decision can be made based on print order data thatspecifies the use of an image that has an inverse mask applied inregistration with the color toner images. In other embodiments, printercontroller 82 can determine that an inverse mask toner image is to beapplied to whenever printer controller 82 determines that an image is tobe formed having a glossy appearance. However, it will be appreciatedprint order information indicating that an image is to be printed with amatte or semi-gloss finish is not necessarily dispositive of the use ofan inverse mask as such an inverse mask can have the effect of removingtoner stack height relief patterns that can create unwanted artifacts inboth matte finishes and semi-gloss finishes.

Printer controller 82 can also be adapted to decide to apply an inversemask in registration with color toner layers in other ways. For example,and again without limitation, printer controller 82 can determine thatan inverse mask toner image is to be applied based on preprogrammedpreferences, based upon document requirements for a series of documentsof which the printing of the image data is required. Any other approachfor determining when an inverse mask toner image is to be applied inregistration with the color toner images can be used.

Where printer controller 82 decides that an inverse mask toner image isto be applied (step 124), inverse mask image processor 112 createsinverse mask image data based upon the color data for a selected one ofthe first set of colors in the image data. The methods used by inversemask image processor 112 in determining the inverse mask image data willbe described in greater detail below. However, it will be immediatelyunderstood that using the determined image data to generate the inversemask image data instead of using the four color separation imagescreated by color separation image processor 110 can reduce an amount ofoverall time required to generate the color separation image data andthe inverse mask image data required for printing.

For example, inverse mask image processor 112 can begin generating theinverse mask image at about the same time that color separation imageprocessor 110 begins processing image data to generate the colorseparation images. It will be further understood that irrespective ofwhen such processing begins, inverse mask image processor 112 cangenerate the inverse mask image during a period of time where the colorseparation image processor 110 is generating the color imageseparations.

The inverse mask image is then supplied to half-tone processor 114 whichconverts the inverse mask image data into screened inverse mask imagedata that can be used by one of the print modules 40-48 in print engine22 to apply toner according to the inverse mask in registration with thecolor toner applied according to the color separation images.

It will be appreciated, however, that the provision and use of half-toneprocessor 114 is optional and that in embodiments of print engine 22having printing modules 40-48 that can form continuous tone images, suchhalf-tone conversion is not necessary. Further, in certain embodimentsthe inverse mask image data can be printed using continuous tone and nothalf-tone printing.

The four half-tone screened color separation images and the inverse maskhalf-tone screen separation image are output appropriate frame buffers(not shown) and provided to printing modules 40-48. This can be donedirectly or by way of appropriate frame buffers or the like. Printercontroller 82 causes these to be printed (step 126). In the exampleembodiment of FIGS. 3 and 4, each printing modules 40-46 apply, inregister, black (K), yellow (Y), magenta (M), and cyan (C) color tonersand printing module 48 applies a inverse mask toner that in this exampletakes the form of a clear toner (CT). Again, methods for generating theinverse mask image for the clear toner (CT) will be described in greaterdetail below.

The printed toner images are then fused and optionally finished inaccordance with any finishing information contained in the printinginformation (step 128.)

It will be appreciated that the embodiment of printer 20 shown in FIG. 3is exemplary only and that any or all functions described herein asbeing performed by any of color separation image processor 110, inversemask image processor 112 and the half-tone processor 114 can be providedby printer controller 82 or by any other suitably programmed computerand/or logic device, and that is adapted to employ stored or generatedthreshold matrices and templates for processing color separation imagesto form half-tone screen separation images having data into renderedimage data in the form of half-tone information suitable for printing.Similarly, the functions ascribed herein as being performed by any ofcolor separation image processor 110 inverse mask image processor 112 orhalf-tone processor 114 can also be provided by an external device 92which conveys color separation images (optionally half-tone screened)and/or inverse mask images to printer controller 82 by way ofcommunication system 90 or by way of other known data conveyancemethods, including but not limited to a removable type of memory 88, orby way of source of image data 108. In other embodiments, printercontroller 82 can perform any or all of the steps of the colorseparation image generating process 130 and the inverse mask imagegenerating process 140 and in such embodiments printer controller 82 canact as for the color separation image processor 110, inverse mask imageprocessor 112 and half-tone processor 114, or portions thereof.

The toner applied to form the inverse mask can be applied before orafter recording of one or more color toners. The toner forming theinverse mask can be clear or otherwise. In the latter case, such tonerwill typically be located below one or more layers of color toner.

Method for Generating Inverse Mask Image

FIG. 4 shows a first embodiment of a method for determining an inversemask image.

As noted above, in the prior art step 132 is a precursor to thedetermination of the inverse mask images. However, as is shown in theembodiment of FIG. 4, an inverse mask toner image is created withoutreference to the color separation image information. Instead, as isshown in FIG. 4, the process for determining an inverse mask toner imagebegins with the receipt of image data for the image to be printed (step142).

The image data for the image to be printed has image data having colordata for a first set of colors used in a first color model. As notedabove, the image data for the image to be printed can have for exampleand without limitation image data that is stored according to the red,green and blue color model as is done in conventional RGB digital imagedata formats or the CMYK color model.

One of the colors of the digital image data is selected for use ingenerating the inverse mask image (step 144). This color can bepredetermined. For example, in certain embodiments, inverse mask imageprocessor 112 can be preprogrammed to use a particular one of the firstset of colors in the first color set for determining the inverse mask.For example, for an image data with color stored according to a red,green and blue color green image data can be used.

Here, green is selected because the toner density used to create imageelements that have high density green content tend to correlate moreclosely to higher toner stack heights formed on a printed receiver thando the other available channels, red and blue. Said another way, highdensity green areas tend to be more indicative of areas of a tonerprinted image that are printed using high density combinations of tonerand therefore areas that also have the highest stack heights. Forsimilar reasons, where the first color model has image data in a CMYKcolor model, the magenta color can be used. Printer 20 can also useother colors when different color models are used and likeconsiderations can be used to select the color used to determine aninverse mask based upon color data stored according to such other colormodels.

It will be appreciated that in many situations the second set of colorsis different from the first set of colors. Accordingly, it can bedifficult to accurately predict an amount of toner of the second set ofcolors that will be required to create a toner image having a particularimage density. However, if the first image data is provided accordingto, for example, a RGB model, the use of the green channel can beadvantageous. This is because the human eye has enhanced sensitivity togreen and, accordingly, the green channel tends to be a reliable proxyfor luminance data in a printed image whether the luminance variationsare created in green or in other color channels. Accordingly, green canbe selected because green color data overall tends to have a densitythat is more proportional generically, to high density printing areashaving relatively large amounts of toner, high toner concentrations orthat have toner stack heights that are relatively high.

Although not benefitting from enhanced visual sensitivity, the use ofthe magenta channel to generate an inverse mask image for image datathat is stored according to the CMYK color model can provide similaradvantages in that high magenta density can serve as a proxy for highdensity printing regions having high overall concentrations of tonerthat are consistent with high toner stack height portions of the image.

In certain embodiments, inverse mask image processor 112 can perform acolor analysis on the image data for each image to be printed as a partof selecting one of the first set of colors. This can be done quicklyusing simple sampling, statistical or histogram analysis techniquesknown to those of skill in the art. This can be done to verify that apredetermined color such as green or magenta is appropriate forselection with regard to a particular image. Specifically, coloranalysis may simply test the image data to determine if there is atleast a minimum threshold of color content of the preselected color inthe image data. Where color analysis indicates that the color content isbelow the threshold, a more general analysis of the color content of theimages can be performed if appropriate.

In another embodiment, inverse mask image processor 112 analyzes thecolor data for each available color in the first set of colors providedin the image data and selects one of the first set of colors for use ingenerating an inverse mask by determining that the selected one of thefirst set of colors has a density that is more proportional to amountsof color toner or to stack heights of color toner that the printer willapply to form the printed images than other colors in the first set ofcolors. In other embodiments, inverse mask image processor 112 canselect one of the colors from the first set of colors that bestcorresponds to the luminance or contrast information in the image datafor the image to be printed. Here too, the selection of a predeterminedfirst one of the colors can be made based on these factors, and inversemask image processor 112 can make such a determination on an image byimage basis.

Inverse mask image processor 112 can perform the color analysis usingthe image data only or it can perform the color analysis on partsthereof using other information stored in the image data or print orderinformation or that can be determined based on such information. Forexample, where the image data is associated with thumbnail informationcontaining a for example a so-called “thumbnail” version of the image asis incorporated in some types of digital image files that contain imagedata, a down sampled version of the image data or information from whichnature or extent of the use of the particular colors in the first set ofcolors can be compared statistically, algorithmically or in other waysto make a determination as to which one of the colors has image datathat is more proportional to an amount of color toner that will beapplied to form the image elements of the image to be printed.

In certain embodiments, it may be useful to perform the process of coloranalysis based on additional factors such as to address printinginstructions that significantly impact the color content of an image,such as printing instructions to mask a portion of an image, to crop outa portion of an image, or to apply a uniform coloration or tint to animage.

Inverse mask image processor 112 then obtains image data for theselected one of the colors of the first set of colors that are availablein the image data for the images to be printed (step 146). Typically,this will involve extracting the image data for the selected color fromthe image data. However, this can be done in any conventional fashionknown for accessing data representing image density for one color of animage data file.

Inverse mask image processor 112 then uses the obtained image data forthe selected color to generate the inverse mask image (step 148). In oneembodiment, inverse mask image processor does this by inverting theimage densities for the selected color. The inverted color image data isthen used as the basis for forming an inverse mask image. Here this isdone by generating an inverse mask image that can be formed or providedin registration with the color toner images and that has a clear tonerimage density that is proportional to the image densities of theinverted image color data for the selected color. Such toner image willhave an inverse mask toner density that is proportional to the imagedensities of the inverted image color data but can be generated withoutdetermining the color separation images for the color toner used to formthe image.

In alternative embodiments, the relationship between image density ofthe selected color at a particular pixel location and a preferred amountof inverse mask image density at that pixel location can vary inaccordance with a predefined non-linear functional relationship, such aswhere a first range of inverse mask image density is used when the imagedensity of the image data for the selected color at the pixel locationis within a first density range, a second range of inverse mask imagedensity is used when the image density of the of the image data for theselected color is at a second density range etc. The precise density fora particular toner used for making an inverse mask image can bedetermined experimentally and will vary depending on the color tonersused and the inverse mask toner used in printing the image.

In some cases, the process of determining an inverse mask image caninclude factors that reduce the overall amount of inverse mask tonerapplied. For example, in certain embodiments an inverse mask image cantarget less than 100% inverse mask toner coverage targeting, instead,70-90 percent. This conserves toner and also provides for reducing thenegative impact on color gamut when clear toner is applied to form theinverse mask in a manner that overlies the colors. Thus, not only costsavings are realized but also, an additional advantage of color gamutmaintenance is obtained. In considering percentage coverage, 100%density by the inverse mask toner implies a representative small area istotally covered with clear toner while for example 90% coverage impliesthat only 90% of the small area is covered. This can be done usinghalf-toning algorithms.

It will be appreciated that alternatively, the inverse mask image can beoptimized to, in addition to the above requirements, reduce gamut lossand may be variable in accordance with the substrate used for thereceiver or process stability.

Inverse Mask Module for Use with a Printer

FIG. 5 illustrates yet another embodiment, wherein an inverse mask imagegenerating module 170 is provided for a printer 20 having a source imagedata 108 providing information from which image data for an image to beprinted can be determined and a print engine 22 for recording tonerimages on a receiver 26 with the image data providing color data for afirst set of colors of a first color model. In this embodiment theinverse mask image generates module 170 which has an input 172 adaptedto receive from the source of image data 108 information from whichimage data for printing can be determined said image data having colordata for a first set of colors used in a first color model. Input 172can comprise any form of wired, wireless, or optical connection that canbe made to source of image data 108 to obtain the image data forprinting, inverse mask image processor 112 that, in this embodiment, canexecute the inverse mask image generating process 140 to generate aninverse mask image using color data for one of the first set of colors.Module 170 also has an output 174 providing the inverse mask image foruse by print engine 22 or a specific module therein. As described above,the inverse mask image can generated based upon the color data for aselected one of the first set of colors so that the inverse mask patterncan be generated without first determining color separation toner imagesthat define amounts of toner to be applied to form the image.

It will be appreciated that the methods and apparatuses described hereincan be used with other types of printers that have a print engine thatdeposits material onto a receiver in layers that build up on a receiverincluding but not limited thermal mass transfer and wax transfersystems.

What is claimed is:
 1. An inverse mask image generating module for aprinter having a source of image data for an image to be printed and aprint engine for recording toner images on a receiver, with the imagedata providing color data for a first set of colors of a first colormodel, with the inverse mask generating module comprising: an inputadapted to receive the image data for an image to be printed from thesource of image data said image data having color data for a first setof colors used in a first color model; an inverse mask image processorgenerating an inverse mask image using color data for one of the firstset of colors; and an output providing the inverse mask image for use bythe print engine; wherein the inverse mask image is generated based uponthe color data for a selected one of the first set of colors so that theinverse mask pattern can be generated without first determining colorseparation toner images that define amounts of color toner to be appliedto a receiver to form the image.
 2. The module of claim 1, wherein theinverse mask image processor generates an inverse mask image using colordata for one of the first set of colors having an image density that ismore proportional to an amount of color toners of that the printer usesto print the image than the other colors in the first set of colors. 3.The printer of claim 1, wherein the toners used to print the image havecolors of a second set of colors that is different from the first set ofcolors.
 4. The module of claim 1, wherein the first set of colorsincludes red, green, and blue., and wherein green color data is used togenerate the inverse mask.
 5. The module of claim 1, wherein the firstset of colors includes cyan, magenta, yellow and black, and whereincolor data for the magenta color is used to generate the inverse mask.6. The module of claim 1, wherein the inverse mask is generated byinverting density information in the color data for the color used togenerate the inverse mask.
 7. The module of claim 1, wherein the colorof the color data used in forming the inverse mask image is determinedby the inverse mask image processor by analyzing the color data for eachof the colors of the first set of colors and, based on the analysis ofthe color data, using color data for the one of the first set of colorsthat is most proportional to an amount of color toner used to form theimage elements of the printed image.
 8. The module of claim 1, whereinthe inverse mask processor generates the inverse mask image using colordata for a color in the first set of colors that the inverse maskprocessor determines has a density that is more proportional to stackheights of color toner that the printer will apply to form the colors ofthe printed image than other colors in the first set of colors.
 9. Themodule of claim 1, wherein the first set of colors includes red, greenand blue and wherein the printer forms the image using a second set ofcolors having cyan, magenta, yellow and black.
 10. The module of claim1, wherein the selected color is the color that best corresponds toluminance information in the image data for the image to be printed. 11.The module of claim 1, further comprising a half-tone processor adaptedto convert inverse mask image into a half-tone screened inverse maskimage.
 12. A printer comprising: a source of image data for an image tobe printed, with the image data providing color data for a first set ofcolors according to a first color model; an inverse mask image processorgenerating an inverse mask toner image based upon the image data; acolor separation image processor converting the image data into colorseparation images for colors of a second set of colors used by a printengine in forming the printed image, with the color separation imagesbeing defined so that after toner is delivered in registration to areceiver according to the color separation images and is fused, thetoner forms the image in the image data; a print engine providing thecolor toner in registered layers according to the determined colorseparation images to form color toner stacks on a receiver and providingthe inverse mask toner according to the inverse mask image to thereceiver in registration with toner applied according to the colortoner; and a fuser for fusing the toner images to the receiver; whereinthe inverse mask image is generated based upon color data for a selectedone of the first set of colors so that the inverse mask can be generatedwithout reference to the color separation images.
 13. The printer ofclaim 12, wherein the color separation image processor converts theimage data into converted image data of a second color model and thecolor separation image processor generates color separation images basedupon the converted image data.
 14. The printer of claim 12, wherein theprinter uses toners having second set of colors that is different fromthe first set of colors.
 15. The printer of claim 12, wherein theinverse mask processor generates the inverse mask image using color datafor a color in the first set of colors that the inverse mask determiningprocessor determines has a density that is more proportional to anamount of color toner that the printer will apply to form the imageelements of the printed image than other colors in the first set ofcolors.
 16. The printer of claim 12, wherein the first set of colorsincludes red, green, and blue and wherein green color data is used togenerate the inverse mask.
 17. The printer of claim 12, wherein thefirst set of colors includes cyan, magenta, yellow and black and whereincolor data for magenta is used to generate the inverse mask.
 18. Theprinter of claim 12, wherein the inverse mask is generated by invertingdensity information in the color data for the color used to generate theinverse mask.
 19. The printer of claim 12, wherein the inverse maskprocessor determines the color to be used in forming the image byanalyzing the color data and, based on the analysis of the color data,using color data for the one of the first set of colors that is mostproportional to the toner stack heights formed in making the image basedon the color content of the image.
 20. The printer of claim 12, whereinthe first set of colors includes red, green and blue and wherein theprinter forms the image using a second set of colors that includes cyan,magenta, yellow and black.
 21. The printer of claim 12, wherein theselected color is the color that best corresponds to luminanceinformation in the image data for the image to be printed.
 22. Theprinter of claim 12, wherein the inverse mask processor generates theinverse mask toner image during a period of time where the colorseparation processor is generating the color toner images.
 23. Theprinter of claim 12, wherein the surface is a surface of the receiver.